4 comments:

And, TB is one of the known factors that causes false positive HIV tests. (Especially when only highly sensitive single ELISA screening tests are used.) (2)

Other than that, how does the guy in question know that '14% of Zambians are HIV positive'? It was once 'common knowledge' that 32.5% of Swazis were 'HIV positive', until a better survey type reduced that to 6%. (3) (This survey type still doesn't use the highly specific (as opposed to sensitive) Western Blot as a confirmation test, which means the final number will be lower still.)

3) Notice how this article tries to claim the positive effects of 'the fight against HIV' for the very different results when using a nationally and statistically representative survey type, as opposed to the usual pregnant women in urban areas survey.

UNICEF DHS IN SWAZILAND

MBABANE, 27 August (PLUSNEWS) - A dramatically lower number of Swazi teenage girls are being infected by HIV than was previously estimated, suggesting a turning point in the battle against HIV/AIDS in a country with the world's highest HIV infection rates.

The findings in the report, 'A Baseline Study on HIV Risk Factors', commissioned by the UN Childrens' Fund (UNICEF) are derived from interviews and blood tests of over 1,000 Swazis in two rural areas and revealed that only six percent of girls aged from 15 to 19 were found to be HIV-positive, with most of the HIV infections occurring among older girls."This is the first time we have had data from a scientifically accurate survey of randomly selected households. It confirms some trends we had suspected, but which were belied by previous HIV estimates," said Dr Alan Brody, country representative for UNICEF.

"This is different from anything that has been seen before. The conventional wisdom is that many more girls were infected," he told PlusNews.

The study was prompted by the results of the government's 2002 sero-surveillance study, which estimated that 32.5 percent of teenage girls between the ages of 15 and 19 were HIV-positive.

Pregnant women at urban antenatal clinics are unrepresentative of the general population for many reasons, on top of which they are pregant, and pregnancy makes all kinds of tests go haywire. On the subject of survey types, see:

" In West Africa, Sierra Leone, just then emerging from a devastating civil war, was found to have a national prevalence rate of less than 1 percent -- compared with an estimated U.N. rate of 7 percent. "

Now these 'estimates' have real world consequences. For instance, if governments believe that HIV infection rates are 20% or more, they will be tempted to divert health resources away from TB and malaria, which means that those diseases start making more victims.

Also, the dramatic HIV infection rates were predicted to affect population growth, which distorts government planning efforts (that is, when they're not determined to leave everything to 'free markets' and actually still plan their development). Roads, schools, hospitals, etc. are all affected by false statistics.

This is how this data was (and still is) arrived at, and it does not inspire confidence - from: Estimates on HIV called too highNew data cut rates for many nationsBy John Donnelly, Globe Staff | June 20, 2004

The tools today are much more refined but still based on a long list of assumptions.

More than a decade ago, AIDS researchers in sub-Saharan Africa found that HIV tests on blood samples from pregnant women at prenatal clinics provided a good indicator of HIV prevalence among adults aged 15 to 49 in countries with high rates; early household surveys confirmed the finding.

But the surveys were limited at first to a few sites in countries. "We were talking about four or five urban sites and one or two rural sites, and extrapolating that to the whole country. You can see what potential inaccuracies there can be with this crude methodology," said Chin, who now is an independent AIDS analyst and criticizes UN estimates as overstated.

Other unknowns contribute to potential errors. One is estimating a country's population; the estimates for Nigeria, for instance, range from 120 million to 160 million people, but a census of the country has not been completed in more than half a century. Another is that most countries do not collect data on deaths.

Once officials from UNAIDS and the WHO arrive at an HIV prevalence estimate for a country, they use that estimate to help determine AIDS deaths, AIDS orphans, numbers of people needing antiretroviral treatment, and the average life expectancy for people in countries. As HIV prevalence numbers are adjusted downward, the numbers for the other AIDS-related categories also will be readjusted similarly.

To estimate the number of people dying from AIDS, for instance, epidemiologists assume that on average a person will live for eight or nine years after infection; they then plot the progression of a country's epidemic, determining how many people were infected in each year. If HIV prevalence estimates are significantly wrong in any year, estimates for AIDS deaths will be correspondingly wrong eight or nine years later.

Some specialists raised questions about the estimates in mid-January, after a report on a household survey in Kenya that estimated a 6.7 percent national HIV prevalence rate, compared with the UN's 15 percent estimate in 2002.

Two weeks later in Addis Ababa, Ethiopia, at a conference on estimating HIV and AIDS prevalence, epidemiologist Peter D. Ghys raised the question of potentially inflated AIDS rates before several dozen epidemiologists. Ghys estimates HIV and AIDS figures for UNAIDS. On the last slide of his presentation, Ghys wrote, "Should UNAIDS/ WHO estimates be lowered by 25 percent?"

Asked recently about his question, Ghys said he raised it in light of the new Kenyan data: "We already had lowered estimates quite a bit in the previous year, but since then, we've had additional information that came in somewhat lower than our estimates. Maybe it will change again, but it's difficult for us to say, yes, it should be 25 percent or something."

In 2003, the UN revised HIV prevalence in sub-Saharan Africa to 26.6 million people, from 29.4 million the year before.

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